1. Field of the Invention
The present invention relates to a wetting solution. More particularly, the present invention relates to a wetting solution for use in a continuous dyeing process for a fabric comprised of synthetic polymer, preferably either polyester or polyamide, fibers characterized by a surface energy of about 18 to 20 dynes per centimeter. The present invention also relates to the continuous dyeing process for treating this fabric.
2. Description of the Prior Art
Continuous dyeing processes for fabric made from synthetic polymer fibers are known. See, for example, U.S. Pat. No. 3,922,141 to Appenzeller et al. and U.S. Pat. No. 4,189,302 to Toland, both of which are hereby incorporated by reference. Such processes typically involve several treating stages. The fabric is initially immersed for prewetting or wetting out in an aqueous solution of a nonionic or anionic surfactant followed by squeezing, e.g., between nip rollers, to a desired wet pickup level. This prewetting step prepares the fabric to permit uniform application and penetration of dye(s). The fabric subsequently has dye(s) applied thereto and is steamed to set the dye(s). Printing and the application of gum may optionally occur prior to dyeing the fabric.
Most wetting solutions utilized in a continuous dyeing process are incapable of completely prewetting, in the short time available, a tufted fabric comprised of polyamide fibers characterized by a low surface energy of about 18 to 20 dynes per centimeter. See for examples of some of these fibers U.S. Pat. No. 4,134,839 to Marshall; U.S. Pat. No. 4,190,545 to Marshall et al.; U.S. Pat. No. 4,192,754 to Marshall et al.; U.S. Pat. No. 4,193,880 to Marshall; and U.S. Pat. No. 4,209,610 to Mares et al.; and U.S. Application No. Ser. No. 102,588 filed Dec. 12, 1979, now U.S. Pat. No. 4,283,292 all of which are hereby incorporated by reference. After being dyed, these fibers, when looked at in side elevation, have color at their tips and roots but not in between. It is believed that this is due to the wetting solution beading up initially and then going to the bottom of the fiber where it is held due to the capillary action between the fiber and fabric backing; when dye is applied, it appears at these two extremes. Even the use of faster wetting surfactants, e.g., sodium dioctyl sulfosuccinate, does not promote the formation of a uniform film of liquid on the fiber surface.